1. Field of the Invention
The present invention relates to a semiconductor laser device and an illumination apparatus using the same.
2. Description of the Related Art
Semiconductor laser devices are used in, for example, light source apparatuses, illumination apparatuses and the like. A semiconductor laser element is provided with a light diffusing member at a light emitting portion thereof so that a scattered light is obtained (FIG. 9).
FIG. 9 is a cross-sectional view schematically showing an outline exemplary structure of a conventional semiconductor laser device.
As shown in FIG. 9, a semiconductor laser device 100 comprises a semiconductor laser element 1 and a light diffusing member 2.
In the semiconductor laser element 1, an internal resonance cavity is provided between a light emission surface 1b and a counter surface 1a which serve as reflective mirrors. Light a oscillates between the two surfaces to form a laser. Laser emission light b emitted from the light emission surface 1b is input to the light diffusing member 2.
The light diffusing member 2 comprises a base material, such as a resin or the like, which contains a scattering material c, such as air bubbles or microparticles (e.g., graphite, carbon, platinum, alumina, etc.). The incoming light b is scattered by the scattering material C, and is emitted as light d from a side surface of the light diffusing member 2 to the outside.
For example, Japanese Laid-Open Publication No. 5-27121 discloses a light source apparatus which comprises an optical fiber and a light source. The optical fiber has a core with a diameter of 0.1 to 5 times the wavelength of the guided light. The optical fiber contains a scattering material. Light emitted by the light source is input to the optical fiber from one end surface thereof. Light scattered in the optical fiber is taken out from a side surface of the optical fiber.
Japanese Laid-Open Publication No. 61-288479 discloses a semiconductor laser device comprising a semiconductor element and a semiconductor laser element. A side surface of the semiconductor element faces parallel to a laser light emitting facet of the semiconductor laser element with a distance of several millimeters or less therebetween. The side surface of the semiconductor element is a cleavage plane and at least a portion thereof is covered with a dielectric reflective film which feeds laser light back to the semiconductor laser element.
Japanese Laid-Open Publication No. 7-192517 discloses an illumination apparatus for roadway guidance of a vehicle. The apparatus is a long-length illumination means comprising a light source and a linear light transmission means connected thereto. Light transmitted through the light transmission means is scattered continuously or intermittently along the line. The apparatus is embedded in a trench formed in a road.
In the conventional semiconductor laser device of FIG. 9, however, light e passing through the light diffusing member 2 cannot be used as scattered light d, resulting in low light emission efficiency.
Also in the conventional light source apparatus of Japanese Laid-Open Publication No. 5-27121 and the illumination apparatus for roadway guidance of a vehicle of Japanese Laid-Open Publication No. 7-192517, light passing through the optical fiber cannot be used as illumination light, resulting from low light emission efficiency. Moreover, these light source apparatuses and the illumination apparatus for roadway guidance of a vehicle do not use an external resonance cavity. Therefore, the laser light is not efficiently used.
The semiconductor laser device of Japanese Laid-Open Publication No. 61-288479 mainly functions as a light detector. A portion of light emitted from a rear surface of the semiconductor laser element is used for light detection, and the remaining light is fed back to the semiconductor laser element by a reflective film. However, no light diffusing member is provided at the semiconductor laser element side. Therefore, scattered light for external emission does not occur. It cannot be said that light is efficiently used for external emission.